This application claims the benefit of United Kingdom Application No. 0026121.4 filed Oct. 25, 2000.
The present invention relates to a method and/or apparatus for detecting a predetermined pattern of bits in a bitstream, particularly, though not exclusively, to a synchronization pattern in a bitstream in a magnetic or optical disc (including Digital Versatile Disc (DVD)) read channel to use as a starting point for data recovery.
Synchronization detectors are used in magnetic and optical disc (including DVD) read channels to identify a known fixed pattern in a serial sequence of bits to use as a starting point in recovering the data. The requirement is to identify where in a random sequence of bits a particular known synchronization pattern occurs. The synchronization pattern is chosen such that it could not occur within the user data (i.e., the synchronization pattern typically contains invalid codewords which could not occur xe2x80x9cnaturallyxe2x80x9d). For example, a DVD-RAM address mark could be formed by the following synchronization pattern: (bit 47) 0001 0001 0000 0000 0000 01000100 01 00 0000 0000 0001 0001 (bit 0)
One aspect of the present invention concerns an apparatus for detecting a predetermined pattern of bits in a data bitstream. The apparatus comprises a series of detecting elements coupled in a series configuration corresponding to a predetermined bit in the predetermined pattern of bits. Each detecting element may be configured to present an output configured to indicate a number of mismatches between (i) the data bit received at the first input in a current detecting element and (ii) the corresponding predetermined bit in the predetermined pattern of bits received at the second input in previous detecting elements.
It is therefore an object of the present invention to provide a synchronization detector which can be used to identify a synchronization pattern in a data bitstream such that a defined point of the user data can be determined.